**Annex 33. Item 10.3.2. – Section 2.2.1. and 2.2.2. of Chapter 2.4.4. Infection with *M. refringens***

CHAPTER 2.4.4.INFECTION WITH *MARTEILIA REFRINGENS*

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2.2.	Host factors

2.2.1.	Susceptible host species

*~~Oyster~~*~~species: *Ostrea edulis* (Grizel *et al*., 1974);**and mussel species:*Mytilus* species including *M. edulis* (Le Roux *et al*., 2001) and *M. galloprovincialis* (López-Flores *et al*., 2004; Novoa *et al*., 2005; Robledo *et al*., 1995a; Villalba *et al*., 1993b).~~

~~Infection with *M. refringens* was demonstrated in the oyster *Ostrea stentina*, the clam species *Solen marginatus*(López-Flores *et al*., 2008a) and *Chamelea gallina* (López-Flores *et al*., 2008b) and the mussel *Xenostrobus securis*(Pascual *et al*., 2010).~~

~~Other *Ostrea*species including*O. chilensis, O.**puelchana, O. angasi*, and*O. denselamellosa* were found to be infected with *Marteilia*sp*.*when deployed in an infected area (Berthe *et al*., 2004; Martin, 1993). However, in these cases, the parasite identification was not done at the molecular level.~~

~~In addition, different stages, including mature stages, of parasites looking like *M. refringens,* were observed by histology in cockles (*Cerastoderma edule*), clam species (*Ruditapes decussatus**R. philippinarum*, *Tapes rhomboides*, *T. pullastra*, *Ensis minor, E. siliqua*), and oysters (*Crassostrea virginica*) among other bivalve species (Berthe *et al*., 2004; López-Flores *et al*., 2008b). In all these cases, parasite identification is uncertain.~~

~~Lastly, the copepod *Paracartia grani* was shown to be susceptible to *M. refringens* and this species could participate in the transmission of the parasites between bivalves (see 2.3.1)~~

Species that fulfil the criteria for listing as susceptible to infection with *Marteilia refringens*according to Chapter 1.5. of the *Aquatic Animal Health Code* (*Aquatic Code*) are: blue mussel (*Mytilus edulis*), dwarf oyster (*Ostrea stentina*), European flat oyster *(Ostrea edulis)*, European razor clam (*Solen marginatus*), golden mussel (*Xenostrobus securis*), Mediterranean mussel (*Mytilus galloprovincialis*) and striped venus clam (*Chamelea gallina*).

Additionally, a copepod species (*Paracartia grani*) has been found to meet the criteria for listing as susceptible to infection with *Marteilia refringens*and is considered an intermediate host.  

2.2.2.	~~Susceptible stages of the host~~Species with incomplete evidence for susceptibility

~~Juveniles and older life stages are known to be susceptible (Grizel, 1985).~~

Species for which there is incomplete evidence to fulfil the criteria for listing as susceptible to infection with *M.refringens* according to Chapter 1.5. of the *Aquatic Code* are: Chilean flat oyster (*Ostrea chilensis*), a copepod (*Paracartia latisetosa*) and Japanese flat oyster (*Ostrea denselamellosa*).

In addition, pathogen-specific positive polymerase chain reaction (PCR) results have been reported in the following species, but no active infection has been demonstrated: Cortez oyster (*Crassostrea corteziensis*), grooved carpet shell (*Ruditapes decussatus*), Pacific cupped oyster (*Magallana*[syn. *Crassostrea] gigas*) and zooplankton (*Acartia discaudata, Centropages typicus*, *Euterpina acutifrons*, unidentified *Oithona sp*., *Penilia avirostris*).  

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